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Coma Panel >> Anion Gap Test
Anion Gap Test

What is anion gap test?
Anion gap test is a blood test which measures the difference between anions and cations in blood

What are anions and cations and why they are important?
Molecules with a charge are called ions. Ions are of two types; cations are positively charged ions, and anions are negatively charged ions. A simple example of a cation and anion is table salt, NaCl or sodium chloride win which sodium is a cation and chloride is anion. Cations and anions are important as they keep an optimal acid-base balance (pH) in our blood and other body fluids.

Why this test is done?

  • To distinguish types of metabolic acidosis.
  • To monitor kidney function
  • To monitor total parenteral nutrition in patients who are in coma

What is metabolic acidosis?
Metabolic acidosis is a condition in which there is too much acid in the body fluids. It usually occurs when the body produces too much acid, or when the kidneys are not removing enough acid from the body. There are several types of metabolic acidosis.

What is parenteral nutrition?
When, because of some disease, medical emergency, surgery or due to any other inevitable reason, you are unable to eat, nutrition must be supplied in a different way. One method is ˇ°parenteral nutritionˇ±, also known as intravenous nutrition.

What will the results of anion gap test tell me?

Normal range: 6-16 mEq/L (or mM/L) (Without calculating in potassium)

Higher range: Common causes of an elevated Anion Gap include:

  • Diabetes
  • Alcohol intoxication or over dose
  • Liver failure
  • Kidney failure
  • Starvation
  • Lung failure
  • Inability to excrete acids (sulfate and phosphate) due to kidney disease
  • Dehydration.
  • Medications such as salicylates

Lower range: The Anion Gap is decreased due to overproduction of alkaloids. Other causes include

  • Alkalosis for any reason (increased blood pH)
  • Excess chloride in blood
  • Low blood sodium level
  • Lithium toxicity (can be due to effects on sodium)
  • Hypothyroidism (Underactive thyroid gland)
  • Kidney disease (due to the loss of the cations sodium and or potassium)

How anion gap test is done?

As with other tests, a small blood sample (usually 5 mL) is taken from a vein in the arm or hand and is then sent or preserved for further analysis.

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